Puja Darbari has joined the children's charity as assistant director of communications, in charge of media relations and campaigns.
She will lead a team of 23, working across national and regional media, reporting to director of communications Diana Green.
Darbari replaces head of media Cynthia Merrilees, who is moving to Spain. But Darbari is taking on an expanded role as the charity looks to place more emphasis on communications and campaigns.
Darbari joined the Liberal Democrats in July 2006, acting as press secretary first for Campbell, then for acting leader Vince Cable. She left in December last year to travel and freelance.
Before the Lib Dems she was employed in the agency world, working as an account director at Forster, where she handled corporate work.
Darbari's first major media push at Barnardo's will be the launch of a project that teaches construction skills, such as electrics, plumbing and carpentry, to 14- to 19-year-olds. Children's secretary Ed Balls is scheduled to launch the project this month.
Another ongoing priority for the charity is the End Child Poverty campaign, a coalition of charities chaired by the CEO of Barnardo's, Martin Narey.
The coalition has told the Government that it will fail to achieve its goal of halving child poverty by 2010 without significant investment.